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Amylase release from streptolysin O permeabilized fetal pancreatic acini
D J Cher1, P J Padfield, J D Jamieson
1Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510.
Insights
Calcium-dependent amylase release from rat pancreatic acini is suppressed at birth but reappears neonatally. This developmental regulation involves sensitivity to modulators like guanosine 5'-O-(3-thiotriphosphate) (GTPγS) and adenosine 3',5'-cyclic monophosphate (cAMP).
Area of Science:
- Endocrinology
- Cell Biology
- Developmental Biology
Background:
- Pancreatic acinar cells secrete digestive enzymes, primarily amylase.
- Protein secretion is regulated by intracellular calcium (Ca2+) levels.
- Developmental changes in pancreatic function are not fully understood.
Purpose of the Study:
- To investigate the developmental regulation of Ca2+-dependent protein discharge in rat pancreatic acini.
- To explore the role of specific signaling molecules in fetal and neonatal pancreatic secretion.
Main Methods:
- Permeabilization of fetal and neonatal rat pancreatic acini using streptolysin O.
- Incubation in a controlled buffer system to measure Ca2+-dependent amylase release.
- Assessment of the effects of ATP depletion, guanosine 5 -O-(3-thiotriphosphate) (GTPγS), 12-O-tetradecanoylphorbol 13-acetate (TPA), and adenosine 3 -cyclic monophosphate (cAMP).
Main Results:
- Ca2+-dependent amylase release was observed in day 19-20 fetal acini but not in term (day 21) fetal acini.
- Amylase release resumed in day 1, 2, and 6 neonatal pancreases.
- ATP depletion inhibited Ca2+-stimulated release in fetal and adult acini.
- GTPγS and TPA enhanced Ca2+-dependent release in day 20 fetal acini.
- Adult acini showed Ca2+-independent GTPγS-stimulated release, unlike fetal acini.
- cAMP had minimal effect on fetal acini release compared to adult acini.
Conclusions:
- The fetal pancreas is capable of Ca2+-dependent protein secretion, which is suppressed around birth.
- Neonatal pancreatic acini regain Ca2+-dependent secretory function.
- Fetal pancreatic acinar cells are sensitive to exocytosis modulators but exhibit different responses compared to adult cells.
Abstract:
Developmental regulation of Ca(2+)-dependent protein discharge was investigated in fetal and neonatal rat pancreatic acini permeabilized with streptolysin O. When incubated at 37 degrees C in a Ca(2+)-ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid/K glutamate buffer, permeabilized day 19 and 20 fetal acini demonstrated Ca(2+)-dependent release of amylase, whereas day 21 (term) fetal acini did not. Ca(2+)-dependent amylase release reappeared in day 1, 2, and 6 neonatal pancreases. ATP depletion completely inhibited Ca(2+)-stimulated amylase release from both day 20 fetal and adult acini. Ca(2+)-dependent amylase discharge from day 20 fetal acini was enhanced by the nonhydrolyzable GTP analogue, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S), and by the phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (TPA). Ca(2+)-independent GTP gamma S-stimulated amylase release was observed from adult but not from day 20 fetal acini. In contrast to its stimulatory effects in permeabilized adult acini, adenosine 3',5'-cyclic monophosphate (cAMP) alone had little effect on release from permeabilized day 20 fetal acini. Our studies indicate that the fetal pancreas is competent to undergo Ca(2+)-dependent protein secretion but that this secretion is suppressed at birth. Our studies also suggest that the fetal gland is sensitive to modulators of exocytosis active in the adult pancreas, such as GTP gamma S, TPA, and cAMP but responds differently to these agents compared with responses in adult glands.